We really love seltzer. So much so that we were accumulating a ridiculous amount of plastic bottles. Lo and behold, we came across the Sodastream and so we ordered one.
Right now I have two bottles of seltzer with fresh lemon sitting in my fridge. They do send you flavor packets so you can make cola or cream sodas, but I prefer regular. The cool thing is you can carbonate apple juice or cranberry juice as well.
For just regular seltzer, you fill the bottle with water up to the fill line and after a few pumps of the button on the machine, Voila! you have carbonated water. My hubby got us a red machine, one of my favorite colors, and I am quite pleased with it.